This section provides background information related to the present disclosure which is not necessarily prior art.
Refrigeration systems utilizing carbon dioxide (CO2) as a refrigerant can have many advantages over refrigeration systems utilizing non-CO2 refrigerants. Refrigeration systems utilizing CO2 refrigerant may include, for example, one or more compressors, a gas cooler, a liquid receiver, and one or more evaporators. The liquid receiver may include a bypass line to discharge refrigerant from the liquid receiver back to the compressors, thereby bypassing the evaporators.
In a refrigeration system utilizing non-CO2 refrigerant, the compressors discharge high pressure gaseous refrigerant to a condenser which cools the refrigerant to below its critical point, resulting in a change in state of the refrigerant from gas to liquid.
In a CO2 refrigeration system operating in a transcritical mode, on the other hand, the gaseous refrigerant is cooled in a gas cooler to a temperature that is still above the critical point of the refrigerant, resulting in a cooler gaseous refrigerant but not resulting in a change in state to liquid. The CO2 refrigerant is then discharged from the gas cooler to a liquid receiver connected to the evaporators and also connected to a bypass line. The pressure of the liquid receiver can be maintained to allow liquid refrigerant to form in the liquid receiver. Liquid refrigerant can then be supplied from the liquid receiver to the evaporators. Gaseous refrigerant in the liquid receiver can then be routed back to the compressors.
Because of the higher operating temperatures and pressures associated with CO2 refrigeration systems, maintaining proper and efficient operation of the refrigeration system can be difficult.